That was announced by President Francois Hollande at the UN General Assembly in New York on Monday, in a bid to leverage more action.
The host nation of this December’s critical Paris climate summit will also increase the amount available as grants, and not as loans, he said.
“We need developed countries to take on financial commitments… we have to make sure that emerging economies, developing countries can be sure they will be helped.”
Hollande noted that the developed world had yet to deliver on its promise to raise US$100 billion of climate finance in 2020.
It is one of three essential conditions he set out for success in Paris, where nearly 200 states are set to sign a carbon-cutting pact.
“Between now and Paris in two months’ time, we will have to continue mobilising finance through the World Bank, development banks, private banks and states to make sure we do reach that level.”
The increased offer from France followed a UK pledge on Sunday to deliver £5.8 billion (US$8.8bn) over 2016-2020, a 50% increase on the previous five years.
Germany promised in May to double its contribution from €2 billion to €4 billion (US$4.5bn) by the end of the decade.
And China last week said it would launch a South-South climate cooperation fund with 20 billion yuan (US$3.1bn), to support poorer countries.
Oxfam welcomed the developments, which it said would put pressure on other donors to follow suit.
“A few other countries, particularly in Europe, I think we can safely expect to pledge more,” the aid agency’s Romain Benicchio told Climate Home.
He also hailed France’s move towards giving grants, which currently account for just 7% of support. The rest comes in the form of loans at concessionary rates.
The shift is set to increase the amount available to help the world’s poorest adapt to the impacts of climate change.
Projects like flood defences and drought-resistant crops have proved harder to finance than clean energy, for example, as they have less certain returns.
Andrew Steer, CEO of Washington-based think tank WRI said the fresh financial commitments were “injecting momentum into the climate talks”.
“As President Hollande has said, a global climate agreement won’t be possible without adequate financial support for developing countries,” he said.
“With these announcements, the governments of France and the UK are showing determination to achieve a successful outcome at the COP in Paris.”